Collapsible saws are known in the prior art. The following United States patents are the most relevant prior art that I know of:
U.S. Pat. No. 3,149,652 issued to Swenson discloses a saw with a channel frame, a tubular handle, and a sawblade. The assembled saw is triangular in form. To collapse the saw, the handle slips transversely off the channel frame, the blade swings into storage position within the channel frame, and the handle then slips longitudinally over the channel frame and blade.
U.S. Pat. No. 4,580,344 issued to Jinghage discloses a saw with a channel frame, a hinged handle, and a sawblade. The assembled saw is triangular in form. To collapse the saw, the blade disconnects from the handle and swings into storage position within the channel frame, and the handle then swings on its hinge to a position alongside the frame.